中文摘要：

提出一种针对复杂可修系统确定预防性维修时间的方法．定义寿命周期，建立工作时间和维修时间的联合密度函数．考虑系统正常运行过程中产生的收益和各种维修活动所造成的损失，应用随机变量函数的数学期望的相关理论，计算单位寿命周期内系统运行单位时间的平均收益关于预防性维修时间丁的函数，以最大单位时间收益为目标对T进行优化．运用Newton迭代法确定系统的最佳预防维修时间，并计算最佳预防维修时间所对应的可靠性．通过实例具体说明所提出预防性维修时间确定方法的建模求解过程，并分析系统寿命分布参数对最佳预防性维修时间的影响．

英文摘要：

A method was proposed to determine preventive maintenance time for repairable and maintainable systems. The life cycle was defined by building the joint density function of working time and maintenance time. Considering the profit during working time and the loss during maintenance time, the function between unit time profit expectation and preventive maintenance time T in a life cycle was confirmed by applying the theory of mathematical expectation of random variable function. The optimal objective is to maximize the unit time profit expectation. Newton＇s method was used to confirm the optimal preventive maintenance time, then the corresponding reliability would be confirmed based on the optimal objective. A numerical example showed that the proposed model is valid. The distribution parameter effect on the optimum preventive maintenance time was analyzed.